Sweetlips are a genus of grunts, thus they belong to the Haemulidae family. The specified subfamily is Plectorhinchinae and the actual genus name is Plectorhinchus. There exists at least 29 different species of sweetlips. These are largely a marine fish, but some species like the harlequin sweetlips can be found in brackish waters. They inhabit the Indian and Western Pacific Oceans, including places like the Red Sea, Seychelles, Solomon Islands and Papua New Guinea. Sweetlips prefer coral-rich lagoons and seaward reefs habitats, especially with edges and caves to hide among during the day. A depth range of 1-30 m seems to be a preference for numerous species, although some such as the trout sweetlips can be found anywhere between 20-200 m at depth. Most species of sweetlips are nocturnal and forage for smaller fish, crustaceans, mollusks and other benthic invertebrates at night.
Sweetlips come in a variety of vivid colorations based on the species. Coloration also changes as the fish matures. For example, the harlequin sweetlips have a brown body with large wide blotches as juveniles, but the adults have a white body with numerous small brown spots. The more defining feature of sweetlips is their large rubbery lips that they get their name from. Because these fish are also grunts, they still hold the trademark ability of producing “grunting” noises. This sound is achieved by rubbing their flat teeth plates together and further amplified by their air bladders.
Some species of juveniles, like the spotted sweetlips, have developed a technique for warding off predators. They will wiggle their bodies and move their fins violently to imitate the movement of poisonous flatworms. Sweetlips are oviparous with distinct pairing during breeding periods. Most species live in solitude as adults, although some may be found in pairs or small groups. They are valued as aquarium fish by some aquarists, and some guides suggest establishing them in small groups rather than individually. The IUCN (International Union for Conservation of Nature) lists most species of sweetlips as either of “least concern” or “not evaluated.”